Optically Active Hybrid Materials Based on Natural Spider Silk

In vitro and in vivo investigation of Argiope bruennichi spider silk-based novel biomaterial for medical use

As a natural and biocompatible material with high strength and flexibility, spider silk is frequently used in biomedical studies. In this study, the availability of Argiope bruennichi spider silk as a surgical suture material was investigated. The effects of spider silk-based and commercial sutures, with and without Aloe vera coating, on wound healing were evaluated by a rat dorsal skin flap model, postoperatively (7th and 14th days). Biochemical, hematological, histological, immunohistochemical, small angle x-ray scattering (SAXS) analyses and mechanical tests were performed. A. bruennichi silk did not show any cytotoxic effect on the L929 cell line according to MTT and LDH assays, in vitro. The silk materials did not cause any allergic reaction, infection, or systemic effect in rats according to hematological and biochemical analyses. A. bruennichi spider silk group showed a similar healing response to commercial sutures. SAXS analysis showed that the 14th-day applications of A. bruennichi spider silk and A. vera coated commercial suture groups have comparable structural results with control group. In conclusion, A. bruennichi spider silk is biocompatible in line with the parameters examined and shows a healing response similar to the commercial sutures commonly used in the skin.

Magnetothermal spider silk-based scaffolds for cartilage regeneration

Developing biocompatible, magnetically controlled polymers is a multifunctional solution to many surgical complications. By combining nanoparticle technology with the latest advancements in polymer materials science, we created a multicomponent hybrid system comprised of a robust native spider silk-based matrix; a Mn0.9Zn0.1Fe2O4 nanoparticles coating to provide a controlled thermal trigger for drug release; and liposomes, which act as drug carriers. Fluorescent microscope images show that the dye loaded into the liposomes is released when the system is exposed to an alternating magnetic field due to heating of ferromagnetic nanoparticles, which had a low Curie temperature (40-46°С). The silk matrix also demonstrated outstanding biocompatibility, creating a favorable environment for human postnatal fibroblast cell adhesion, and paving the way for their directed growth. This paper describes a complex approach to cartilage regeneration by developing a spider silk-based scaffold with anatomical mechanical properties for controlled drug delivery in a multifunctional autologous matrix-induced chondrogenesis.

Spiroheterocyclic Photocatalyst for Reducing QHIn-Persistent Pollutants, Dyes, and Transition-Metal Ions Cocatalyzed with Electrolytes

The 7-nitro-2'-phenyl-5',6',7',7a'-tetrahydrospiro[indeno[1,2-b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile (SIQPI), 2'-(4-cyanophenyl)-7-nitro-5',6',7',7a'-tetrahydrospiro[indeno[1,2-b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H) dicarbonitrile (SIQPII), and 2'-(4-methoxyphenyl)-7-nitro-5',6',7',7a'-tetrahydrospiro[indeno[1,2-b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile (SIQPIII) were used to photocatalyze quinonoid phenolphthalein (QHIn) in aq-ACN-EtOH (mixed solvent) with NaCl and KCl electrolytes. SIQPI, II, and III spiroindenoquinoxaline pyrrolidines (SIQPs) as spiroheterocyclic photocatalysts alone could not reduce QHIn, but with the addition of electrolytes they are reduced via π cationic interactions (PCI). SIQPI, II, and III with NaCl reduced QHIn in 120, 28, and 50 min, unlike in 138, 58, and 63 min with KCl in mixed solvent. SIQPI, II, and III alone have reduced methylene blue (MB) in 120, 45, and 70 min, unlike in 110, 27, and 55 min with graphene oxide (GO), whereas with NaCl and KCl hey are reduced in 82, 36, and 44 min and 89, 43, and 50 min, respectively. SIQPs with GO had reduced MB in less time than the SIQPs alone, and SIQPs with NaCl had reduced QHIn in a shorter time than KCl. The electrolytes have cocatalyzed a reduction of dyes under sunlight (SL). The electrolytes have reduced a quinonoid structure (QS) and dyes by generating negative and positive (e - and h +) holes in a shorter time. SIQPII and magnetic nanoparticles (MNPs) of 58 nm with NaCl photocatalyzed the QHIn in 2880 min. The SIQPs also reduced methyl orange (MO) and brilliant blue R (BBR) at variable temperature (T) and pH range, whereas SIQPs have developed a molecular organic framework (MOF) with transition-metal salts (NiCl2, CrO3, KMnO4, CuSO4, and MnCl2) on photocatalysis.

Electroactive aniline tetramer-spider silks with conductive and electrochromic functionality

Electroactive aniline tetramer-spider silk composite fibers with high conductivity and mechanical strength were developed using a dip coating method. The fabricated spider silk composite fibers retain the high mechanical strength (0.92 GPa) and unique reversible relaxation-contraction behavior of spider dragline silks. The aniline tetramer modified on the silk surface imparted electroactive properties to the composite fibers. The color of aniline tetramer/spider silk composite fibers could be controlled by applying different pH values and voltages. Furthermore, the composite fiber's resistivity could reach 186 Ω m which can conduct electrical current to light LEDs. This study could provide a valuable guideline for developing highly-conductive electrochromic spider silks for use in E-textiles.

Functionalization and Reinforcement of Recombinant Spider Dragline Silk Fibers by Confined Nanoparticle Formation

Spider dragline silk is a remarkable protein fiber that is mechanically superior to almost any other natural or synthetic material. As a sustainable supply of natural dragline silk is not feasible, recombinant production of silk fibers with native-like mechanical properties and non-native physiochemical functions is highly desirable for various applications. Here, we report a new strategy for simultaneous functionalization and reinforcement of recombinant spider silk fibers by confined nanoparticle formation. First, a mimic silk protein (N16C) of spider Trichonephila clavipes was recombinantly produced and wet-spun into fibers. Drawing the as-spun fibers in water led to post-drawn fibers more suitable for the templated synthesis of nanoparticles (NPs) with uniform distribution throughout the synthetic fibers. This was exemplified using a chemical precipitation reaction to generate copper sulfide nanoparticle-incorporated fibers. These fibers and the derived fabric displayed a significant photothermal effect as their temperatures could increase to over 40 °C from room temperature within 3 min under near-infrared laser irradiation or simulated sunlight. In addition, the tensile strength and toughness of the nanofunctionalized fibers were greatly enhanced, and the toughness of these synthetic fibers could reach 160.1 ± 21.4 MJ m^-3, which even exceeds that of natural spider dragline silk (111.19 ± 30.54 MJ m^-3). Furthermore, the confined synthesis of gold NPs via a redox reaction was shown to improve the ultraviolet-protective effect and tensile mechanical properties of synthetic silk fibers. These results suggest that our strategy may have great potential for creating functional and high-performance spider silk fibers and fabrics for wide applications.

Metal-Nanostructure-Decorated Spider Silk for Highly Sensitive Refractive Index Sensing

Highly sensitive detection of refractive index (RI) is essential for the analysis of the bio-microenvironment and basic cellular reactions. To achieve this, optic-fiber RI sensors based on localized surface plasmon resonance (LSPR) have been widely used for their flexibility and high sensitivity. However, the current optic-fiber RI sensors are mainly fabricated using glass, which makes them face the challenges in biocompatibility and biosafety. In this work, a RI sensor with high sensitivity is fabricated using metal-nanostructure-decorated spider silk. The spider silk, which is directly dragged from Araneus ventricosus, is natural protein-based biopolymer with low attenuation, good biocompatibility and biodegradability, large RI, great flexibility, and easy functionalization. Hence, the spider silk can be an ideal alternative to glass for sensing in biological environments with a wide RI range. Different kinds of metal nanostructures, such as gold nanorods (GNRs), gold nanobipyramids (GNBP), and Ag@GNRs, are decorated on the surface of the spider silk utilizing the surface viscidity of the silk. By directing a beam of white light into the spider silk, the LSPR of the metal nanostructures was excited and a highly sensitive RI sensing (the highest sensitivity of 1746 nm per refractive index was achieved on the GNBP-decorated spider silk) was obtained. This work may pave a new way to precise and sensitive biosensing and bioanalysis.

Modulating Surface Properties of the Linothele fallax Spider Web by Solvent Treatment

Linothele fallax (Mello-Leitão) (L. fallax) spider web, a potentially attractive tissue engineering material, was investigated using quantitative peak force measurement atomic force microscopy and scanning electron microscopy with energy dispersive spectroscopy both in its natural state and after treatment with solvents of different protein affinities, namely, water, ethanol, and dimethyl sulfoxide (DMSO). Native L. fallax silk threads are densely covered by globular objects, which constitute their inseparable parts. Depending on the solvent, treating L. fallax modifies its appearance. In the case of water and ethanol, the changes are minor. In contrast, DMSO practically removes the globules and fuses the threads into dense bands. Moreover, the solvent treatment influences the chemistry of the threads' surface, changing their adhesive and, therefore, biocompatibility and cell adhesion properties. On the other hand, the solvent-treated web materials' contact effect on different types of biological matter differs considerably. Protein-rich matter controls humidity better when wrapped in spider silk treated with more hydrophobic solvents. However, carbohydrate plant materials retain more moisture when wrapped in native spider silk. The extracts produced with the solvents were analyzed using nuclear magnetic resonance (NMR) and liquid chromatography-mass spectrometry techniques, revealing unsaturated fatty acids as representative adsorbed species, which may explain the mild antibacterial effect of the spider silk. The extracted metabolites were similar for the different solvents, meaning that the globules were not "dissolved" but "fused into" the threads themselves, being supposedly rolled-in knots of the protein chain.

Upconversion Nanoparticle Decorated Spider Silks as Single-Cell Thermometers

Noninvasive and sensitive thermometry of a single living cell is crucial to the analysis of fundamental cellular processes and applications to cancer diagnosis. Optical fibers decorated with temperature-sensitive nanomaterials have become widely used instruments for biosensing temperature. However, current silica fibers exhibit low compatibility and degradability in biosystems. In this work, we employ spider silks as natural optical fibers to construct biocompatible thermometers. The spider silks were drawn directly from Araneus ventricosus and were decorated with core-shell upconversion nanoparticles (UCNPs) via a photophoretic effect. By measuring the fluorescence spectra of the UCNPs on the spider silks, the membrane temperature of a single breast cancer cell was obtained with absolute and relative sensitivities ranging from 3.3 to 4.5 × 10^-3 K^-1 and 0.2 to 0.8% K^-1, respectively. Additionally, the temperature variation during apoptosis was monitored by the thermometer in real time. This work provides a biocompatible tool for precise biosensing and single-cell analysis.

Hybrid Spider Silk with Inorganic Nanomaterials

High-performance functional biomaterials are becoming increasingly requested. Numerous natural and artificial polymers have already demonstrated their ability to serve as a basis for bio-composites. Spider silk offers a unique combination of desirable aspects such as biocompatibility, extraordinary mechanical properties, and tunable biodegradability, which are superior to those of most natural and engineered materials. Modifying spider silk with various inorganic nanomaterials with specific properties has led to the development of the hybrid materials with improved functionality. The purpose of using these inorganic nanomaterials is primarily due to their chemical nature, enhanced by large surface areas and quantum size phenomena. Functional properties of nanoparticles can be implemented to macro-scale components to produce silk-based hybrid materials, while spider silk fibers can serve as a matrix to combine the benefits of the functional components. Therefore, it is not surprising that hybrid materials based on spider silk and inorganic nanomaterials are considered extremely promising for potentially attractive applications in various fields, from optics and photonics to tissue regeneration. This review summarizes and discusses evidence of the use of various kinds of inorganic compounds in spider silk modification intended for a multitude of applications. It also provides an insight into approaches for obtaining hybrid silk-based materials via 3D printing.

Recent Advances in Development of Functional Spider Silk-Based Hybrid Materials

Silkworm silk is mainly known as a luxurious textile. Spider silk is an alternative to silkworm silk fibers and has much more outstanding properties. Silk diversity ensures variation in its application in nature and industry. This review aims to provide a critical summary of up-to-date fabrication methods of spider silk-based organic-inorganic hybrid materials. This paper focuses on the relationship between the molecular structure of spider silk and its mechanical properties. Such knowledge is essential for understanding the innate properties of spider silk as it provides insight into the sophisticated assembly processes of silk proteins into the distinct polymers as a basis for novel products. In this context, we describe the development of spider silk-based hybrids using both natural and bioengineered spider silk proteins blended with inorganic nanoparticles. The following topics are also covered: the diversity of spider silk, its composition and architecture, the differences between silkworm silk and spider silk, and the biosynthesis of natural silk. Referencing biochemical data and processes, this paper outlines the existing challenges and future outcomes.

A general strategy for designing NIR-II emissive silk for the in vivo monitoring of an implanted stent model beyond 1500 nm

Silk fibroin-based materials spun by silkworms present excellent biocompatible and biodegradable properties, endowing them with broad applications for use in in vivo implanted devices. Therefore, it is highly desirable to explore functionalized silk with additional optical bioimaging abilities for the direct in situ monitoring of the status of implanted devices in vivo. Herein, a new type of silk material with a second near-infrared (NIR-II, 1000-1700 nm) emission is explored for the real-time observation of a biological stent model using a general route of feeding larval silkworms with lanthanide-based NaYF₄:Gd³⁺/Yb³⁺/Er³⁺@SiO₂ nanocrystals. After being fed lanthanide nanocrystals, the silk spun by silkworms shows efficient NIR-II emission beyond 1500 nm. Moreover, NIR-II bio-imaging guided biological stent model monitoring presents a superior signal-to-noise (S/N) ratio compared to the traditional optical imaging by utilizing the upconversion (UC) region. These findings open up the possibility of designing NIR-II optically functionalized silk materials for highly sensitive and deep-tissue monitoring of the in vivo states of the implanted devices.